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Mirror Ball Safety

Discussion in 'Lighting and Electrics' started by tomed101, Aug 13, 2008.

  1. tomed101

    tomed101 Active Member

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    For a show we are doing we need a mirror ball. It occurred to me today when I was hanging it that there is no actual way to safety a mirror ball. On the motor spindle there is only a very small hole, just big enough for the ring on the mirror ball to fit through. Is there a way of doing this, and I just can see it, or is thins just one of those things which people ignore?

    My main concern is that all that is holding up the ball which weighs a few kg's is a split ring (is that what they are called? The things which key rings are made out of) To me it seems like if there was enough pressure on one point for an extended period of time, the ring could open up. We will only have it hung for a few weeks, but even so, that could be enough time.

    What do you guys reckon? Am I just being overly cautious or is there something else I should be using?
     
  2. soundlight

    soundlight Well-Known Member

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    Strong, thick split rings can take a lot of pressure. I worked a gig recently where we had some 16 or so mirror balls, all held to the motors by split rings or similar, and they were up for 3 days and rotating almost continuously for about a full day total. No issues, none of the split rings were bent.

    Definitely safety the motor, though. The ones you want are probably in the odds and ends section of the hardware wall of your local hardware store, not in the arts-and-crafts section of the walmart or the keychain stand in the dollar store.

    I have seen some scarily small split rings in mirror balls, some of those ones that aren't really sprung shut, more just wire that was looped twice to make a keychain. Stay away from these. But I'm sure that you already knew that.
     
  3. LightStud

    LightStud Active Member

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    Baling wire and bubble gum. ;)
     
  4. JD

    JD Well-Known Member

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    I watched a big one come down at a stadium! No one was near it (thankfully) and it beat the heck out of anything you would ever see on David Letterman. ;)

    (the old West Philly Arena, 1979 Ohio Players show. I was working sound that night.)
     
  5. Darthrob13

    Darthrob13 Active Member

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    "Rollercoaster...

    ....of Love....

    Rollercoaster....
    ...ooo...ooo...ooo..."
     
  6. JD

    JD Well-Known Member

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    Yep. Them.

    The night also features a riot when the promoter and band got into a disagreement. Luckily, there was a change of heart just as the pinnacle of ugly was being reached. (unrelated to exploding mirror ball)
     
  7. derekleffew

    derekleffew Resident Curmudgeon Senior Team Premium Member

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    I've personally witnessed two demonstrations of of a mirrored ball's acceleration due to gravity. Both times the split key ring failed when subjected to external force, while the motor remained safely affixed, happily rotating.
     
  8. gafftapegreenia

    gafftapegreenia CBMod CB Mods

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    Hmm, maybe we should figure out a way to affix the mirror ball to the motor using shackles?

    But that's rigging so we can't
     
  9. ship

    ship Senior Team Emeritus Premium Member

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    Most mirror ball motors that are properly sized for the mirror ball have larger shaft holes and or eye bolts even on a swivel so as not to damage the motor after power is off, that allows for the use of real rigging hardware with them. This at least 3/16" shackles or 1/8" quick links at a minimum and up thru there with 1/2" eye bolts used for 60" mirror balls. American DJ's DMX mirror ball motor for instance is not that bad in this way of having about a 3/16" hole.

    In the case of smaller mirror balls, I normally replace the key ring with a 1/16" wire rope - this after having removed the right angle edges from the shaft. 95# Safe Working Load should be enough for up to a 24" mirror ball - though that's pushing it in my opinion.

    In addition to this concern about the mirror ball hanging itself, how you rig that mirror ball motor itself becomes a concern. Most have a cast aluminum frame with four supports or a sheet metal frame that's not much more at best substantial to a shock loading especially if hung from a single or two points instead of all four rig points normally available for such a motor. Not a fan of the center rig point on the above ADJ mirror ball motor for instance, that motor for me gets a 1/8" steel plate and or frame to rig from dependant on the situation.

    Normally I'll build a frame for mounting mirror ball motors - kind of like the frame a marionette would have its wires suspended from if not a solid plate steel with real rig points. The central bar that's lifted up above the plates allow for bolting clamps or eyebolts to it and for running a safety cable under it. 1x1 box steel often gets used for this if not 1/4" plate steel and perhaps Unistrut. Many ways to do such a frame, important point being it supports the mirror ball motor thru all its flanges equally. Absolutely in my opinion necessary if hanging a mirror ball motor to use all of its mounting holes in a way they all equally support not just the weight but the shock load also. Short of lifting it from it's designed hard points - all of them, you are stressing that frame and I have seen mounting flanges crack or break before. From such a frame you than also do the safety cable for it.

    Drywall screws into a plywood plate don't make it with me either.
     

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